Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$185.29	8.131%	$200.3559	$200.36	$200.35	$200.40
Purchase #2	$81.31	10.411%	$89.7752	$89.78	$89.80	$89.80
Purchase #3	$67.95	3.333%	$70.2148	$70.21	$70.20	$70.20
Purchase #4	$139.51	5.692%	$147.4509	$147.45	$147.45	$147.50
Purchase #5	$173.50	9.139%	$189.3562	$189.36	$189.35	$189.40
Purchase #6	$111.58	12.371%	$125.3836	$125.38	$125.40	$125.40
Purchase #7	$174.89	3.237%	$180.5512	$180.55	$180.55	$180.60
7 purchase totals =	$934.03		$1,003.0878	$1,003.09	$1,003.10	$1,003.30